TY  - JOUR
A1  - Werner, Klaus
A1  - Barstow, Martin A.
A1  - Holberg, J. B.
A1  - Koester, D.
A1  - Nousek, J. A.
T1  - Extreme ultraviolet spectroscopy of white dwarfs
Y1  - 1994
ER  - 
TY  - GEN
A1  - Reindl, Nicole
A1  - Finch, Nicolle L.
A1  - Schaffenroth, Veronika
A1  - Barstow, Martin A.
A1  - Casewell, Sarah L.
A1  - Geier, Stephan
A1  - Bertolami Miller, Marcelo Miguel
A1  - Taubenberger, Stefan
T1  - Revealing the true nature of Hen2-428
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines quantitative non-local thermodynamic (non-LTE) equilibrium spectral modelling, radial velocity analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations. Importantly, we find that the dynamical system mass that is derived by using all available He II lines does not exceed the Chandrasekhar mass limit. Furthermore, the individual masses of the two central stars are too small to lead to an SN Ia in case of a dynamical explosion during the merger process.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1129 
KW  - binaries: spectroscopic
KW  - stars: atmospheres
KW  - stars: abundances
KW  - Supernovae
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-459703
SN  - 1866-8372
IS  - 1129
ER  - 
TY  - JOUR
A1  - Reindl, Nicole
A1  - Finch, Nicolle L.
A1  - Schaffenroth, Veronika
A1  - Barstow, Martin A.
A1  - Casewell, Sarah L.
A1  - Geier, Stephan
A1  - Bertolami Miller, Marcelo Miguel
A1  - Taubenberger, Stefan
T1  - Revealing the true nature of Hen 2-428
JF  - Galaxies
N2  - The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines quantitative non-local thermodynamic (non-LTE) equilibrium spectral modelling, radial velocity analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations. Importantly, we find that the dynamical system mass that is derived by using all available He II lines does not exceed the Chandrasekhar mass limit. Furthermore, the individual masses of the two central stars are too small to lead to an SN Ia in case of a dynamical explosion during the merger process.
KW  - binaries: spectroscopic
KW  - stars: atmospheres
KW  - stars: abundances
KW  - supernovae
Y1  - 2018
U6  - https://doi.org/10.3390/galaxies6030088
SN  - 2075-4434
VL  - 6
IS  - 3
ER  - 
TY  - JOUR
A1  - Fusillo, Nicola Pietro Gentile
A1  - Tremblay, Pier-Emmanuel
A1  - Gänsicke, Boris T.
A1  - Manser, Christopher J.
A1  - Cunningham, Tim
A1  - Cukanovaite, Elena
A1  - Hollands, Mark
A1  - Marsh, Thomas
A1  - Raddi, Roberto
A1  - Jordan, Stefan
A1  - Toonen, Silvia
A1  - Geier, Stephan
A1  - Barstow, Martin
A1  - Cummings, Jeffrey D.
T1  - A Gaia Data Release 2 catalogue of white dwarfs and a comparison with SDSS
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present a catalogue of white dwarf candidates selected from the second data release of Gaia (DR2). We used a sample of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey (SDSS) to map the entire space spanned by these objects in the Gaia Hertzsprung–Russell diagram. We then defined a set of cuts in absolute magnitude, colour, and a number of Gaia quality flags to remove the majority of contaminating objects. Finally, we adopt a method analogous to the one presented in our earlier SDSS photometric catalogues to calculate a probability of being a white dwarf (PWD) for all Gaia sources that passed the initial selection. The final catalogue is composed of 486641 stars with calculated PWD from which it is possible to select a sample of ≃260000 high-confidence white dwarf candidates in the magnitude range 8 < G < 21. By comparing this catalogue with a sample of SDSS white dwarf candidates, we estimate an upper limit in completeness of 85 per cent for white dwarfs with G ≤ 20 mag and Teff >7000 K, at high Galactic latitudes (|b| > 20°). However, the completeness drops at low Galactic latitudes, and the magnitude limit of the catalogue varies significantly across the sky as a function of Gaia’s scanning law. We also provide the list of objects within our sample with available SDSS spectroscopy. We use this spectroscopic sample to characterize the observed structure of the white dwarf distribution in the H–R diagram.
KW  - catalogues
KW  - surveys
KW  - white dwarfs
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty3016
SN  - 0035-8711
SN  - 1365-2966
VL  - 482
IS  - 4
SP  - 4570
EP  - 4591
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - GEN
A1  - Finch, Nicolle L.
A1  - Braker, I. P.
A1  - Reindl, Nicole
A1  - Barstow, Martin A.
A1  - Casewell, Sarah L.
A1  - Burleigh, M.
A1  - Kupfer, Thomas
A1  - Kilkenny, D.
A1  - Geier, Stephan
A1  - Schaffenroth, Veronika
A1  - Bertolami Miller, Marcelo Miguel
A1  - Taubenberger, Stefan
A1  - Freudenthal, Joseph
T1  - Spectral Analysis of Binary Pre-white Dwarf Systems
T2  - Radiative signatures from the cosmos
N2  - Short period double degenerate white dwarf (WD) binaries with periods of less than similar to 1 day are considered to be one of the likely progenitors of type Ia supernovae. These binaries have undergone a period of common envelope evolution. If the core ignites helium before the envelope is ejected, then a hot subdwarf remains prior to contracting into a WD. Here we present a comparison of two very rare systems that contain two hot subdwarfs in short period orbits. We provide a quantitative spectroscopic analysis of the systems using synthetic spectra from state-of-the-art non-LTE models to constrain the atmospheric parameters of the stars. We also use these models to determine the radial velocities, and thus calculate dynamical masses for the stars in each system.
Y1  - 2019
SN  - 978-1-58381-925-8
SN  - 1050-3390
VL  - 519
SP  - 231
EP  - 238
PB  - Astronomical soc pacific
CY  - San Fransisco
ER  -